renice

Alters the scheduling priority/nicenesses of one or more running processes. Niceness values range from -20 (most favorable to the process) to 19 (least favorable to the process).

Change priority of a running process:

renice -n {{niceness_value}} -p {{pid}}

Change priority of all processes owned by a user:

renice -n {{niceness_value}} -u {{user}}

Change priority of all processes that belong to a process group:

renice -n {{niceness_value}} --pgrp {{process_group}}